Mtd riding mowers not going into gear stuck in nutral

Are your sure the Clutch is actually releasing? Which in many cases only tightens or loosens a drive belt. I assume its stuck when running and not stuck with it off.

Hi,
If the machine was stopped without engaging the clutch, the belts could be wedged in the variable speed pulley. To cure that, put in fastest speed and neutral, crank engine, release the clutch and when you hear the sound of the pulley spinning it will be fixed. Then push in clutch and attempt to put in gear.
Peace,
Clarke